1. Field of the Invention
The invention relates to a wheel bearing device for supporting a wheel of an automobile and a method of manufacturing the same.
2. Description of the Related Art
Wheel bearing devices are broadly divided into two categories: those for driving wheels, and those for driven wheels. For example, in a wheel bearing device for driving wheels, as FIG. 33 shows, a hub ring 100, a bearing 200, and a constant velocity universal joint 400 are unitized together. Further, of inner raceways of the bearing 200 in double rows, one of the inner raceways, or an inner raceway 270, is formed at the hub ring 100, and the other inner raceway, or an inner raceway 280, is formed at an outer joint member 410 of the constant velocity universal joint 400.
The hub ring 100 has a flange 140 for supporting a wheel, and the inner raceway 270 is formed at an outside periphery, near the flange 140, of the hub ring 100. The outer joint member 410 of the constant velocity universal joint 400 comprises a mouth portion 460 of a bowl shape and a solid stem portion 450, and is fitted on the hub ring 100 at the stem portion 450 through serration. A shoulder portion 470 of the outer joint member 400 is in contact with an end face of the hub ring 100. The inner raceway 280 is formed at a portion of the outer joint member 410, or at an outside periphery of the mouth portion 460 near the stem portion 450. Outer raceways 240 in double rows facing to the inner raceways 270 and 280 are formed at an inside periphery of an outer member 210 of the bearing 200. Further, rolling members 220 in double rows are assembled between the inner raceways 270 and 280 in double rows and the outer raceways 240 in double rows.
As indicated by numeral 450xe2x80x2, an end of the stem portion 450 projecting from the hub ring 100 in an axial direction is bent for swaging to join together the stem portion 450 and the hub ring 100. Further, the outer member 210 is fixed to a suspension device by a fixing portion 230 formed in a flange shape facing outward at an outside periphery of the outer member 210, and a wheel is fixed to the flange 140 of the hub ring 100.
Another example of a wheel bearing device is, as FIG. 34 shows, such that an inner ring 350 is fitted onto a small-diameter cylindrical portion 170 formed at the outside periphery of the hub ring 100. Known as this type of wheel bearing device is such that an end of the small-diameter cylindrical portion 170 of the hub ring 100 projecting from the inner ring 350 in the axial direction is, as denoted by numeral 170xe2x80x2, bent for swaging to join together the inner ring 350 and the hub ring 100.
With the wheel bearing device described above, the bearing is generally given with preload, and precise preload control is made when assembling the bearing. In an automobile, however, large moment load is applied to the bearing portion particularly when it turns. Therefore, in a method where an end of the stem portion 450 of the outer joint member 410 (as shown in FIG. 33) or an end of the small-diameter cylindrical portion 170 (as shown in FIG. 34) is bent and swaged, the swaged portion may loosen owing to a reason such as spring-back at the swaged portion, resulting in a possible change in dimension between the inner raceways in double rows and causing loss of preload.
Therefore, an object of the invention is to prevent loosening at a swaged portion.
Another object of the invention is to provide a method of manufacturing a wheel bearing device that can put preload to the inside of the bearing when swaging for joining, and can easily provide an appropriate amount of preload.
In order to achieve the objects described above, in a wheel bearing device according to the invention, a hub ring, a constant velocity universal joint, and a bearing are unitized together, the hub ring and an outer joint member of the constant velocity universal joint are fitted together, of inner raceways in double rows of the bearing, one of the inner raceways is formed at the hub ring while at the same time the other inner raceway is formed at the outer joint member. Further, a hardened irregular portion is formed at an outside-diameter side member at a fit portion of the hub ring and the outer joint member, and also at the same time, a low hardness portion having a hardness lower than that of the irregular portion is provided at an inside-diameter side member. Then, the low hardness portion is expanded in diameter to make it bite into the irregular portion, so that the hub ring and the outer joint member are unitized together.
When the diameter of the low hardness portion is expanded to make it bite into the irregular portion as described above, joining strength is improved in comparison with conventional swaging made by bending. Consequently, the hub ring and the outer joint member that are fitted together are prevented from loosening, and loss of preload can be avoided.
An effect similar to that described above is obtainable when a hardened irregular portion is provided at the inside-diameter side member. In this case, the irregular portion itself is expanded in diameter to make it bite into a mating face to which the irregular portion is fitted. However, if the irregular portion is excessively hardened, there is fear that swaging cracks occur in a base material of the irregular portion as the diameter is expanded. Therefore, the irregular portion cannot be made too hard; Rockwell hardness (C scale, hereafter as well) of from about HRc 40 to 45 is the limit of the hardness. With such hardness as above, however, the difference in hardness from its mating face of fitting is only about HRc 20 to 25, and therefore the irregular portion may be crushed as it bites into the mating face, causing possible lack in joining strength. As a countermeasure thereto, diameter-expansion allowance (extent of expansion toward an outside-diameter sides of the irregular portion may be increased. In this case, however, when once the irregular portion has bitten into its mating face to a certain depth, the fit portion starts to expands only toward an outside-diameter side afterward without biting into the mating face, thereby producing poor joining force.
On the other hand, when an member (an outside-diameter side member) having the irregular portion as described above and an member (an inside-diameter side member) to be expanded in diameter are arranged as separate members, it is possible to sufficiently harden (to about HRc 60, for example) the irregular portion. With the method described above, the irregular portion is prevented from being crushed in a swaging process and the member to be expanded in diameter can be provided with a low hardness portion having excellent ductility at the same time. Swaging cracks can be prevented from occurring through the expansion of this low hardness portion. Therefore, swaging is made into a deep depth between the hub ring and the outer joint member, so that sufficient joining strength can be secured.
As an embodiment for fitting together the hub ring and the outer joint member, there can be a case where the outside-diameter side member at the fit portion is the hub ring and the inside-diameter side member is the outer joint member (FIG. 1) or a case where the, outside-diameter side member at the fit portion is the outer joint member and the inside-diameter side member is the hub ring (FIG. 7).
Further, a wheel bearing device according to the invention comprises a hub ring and a bearing that are unitized together, the hub ring and an inner ring of the bearing are fitted together, and, of inner raceways in double rows of the bearing, one of the inner raceways is formed at the hub ring while at the same time the other inner raceway is formed at the inner ring. In this wheel bearing device, moreover, a hardened irregular portion is formed at an outside-diameter side member at a fit portion of the hub ring and the inner bring, and also at the same time, a low hardness portion having a hardness lower than that of the irregular portion is provided at an inside-diameter side member. The low hardness portion is expanded to make it bite into the irregular portion, and thereby the hub ring and the inner ring are unitized.
In this case as well, the low hardness portion is expanded in diameter to make it bite into the irregular portion. Accordingly, joining strength higher than that obtainable in a conventional swaging method by bending is achieved and loss of preload can be avoided. Further, because the irregular portion and the member that is expanded in diameter are separate members, the low hardness portion having excellent ductility can be provided at the member of which diameter is expanded while the irregular portion is being given sufficient hardness. Therefore, the low hardness portion can be made to deeply bite into the irregular portion.
As an embodiment for fitting the hub ring and the inner ring together, there can be a case where the outside-diameter side member at the fit portion is the inner ring and the inside-diameter side member is the hub ring (FIG. 8).
The wheel bearing device of the present invention can be used for driving wheels when the outer joint member of the constant velocity universal joint is fitted to the inside periphery of the hub ring in a manner in which torque is transmittable (FIG. 19). In this case, a pilot portion that controls a clearance between the inside periphery of the hub ring and an outside periphery of the outer joint member is provided near a line extended from a line forming a contact angle of rolling members rolling on a inner raceway of the inner ring (FIG. 10). This arrangement prevents deformation of the fit portion of the hub ring and the inner ring caused by load acting in a direction of the line that forms the contact angles As a result, effect such as prevention of breakage of the hub ring and reduction in fretting wear between the hub ring and the inner ring are obtained. Further, deformation of the inner raceway of the inner ring, caused by load in the direction of the line that forms the contact angle, is prevented from occurring, so that effect such as improvement of rolling life can be obtained. To obtain the effects described above, it is preferable that a clearance width of the pilot portion is set at 0.4 mm or less.
When the low hardness portion is expanded in diameter at an inside-diameter side in an area including at least a part of either of the inner raceways, pressing force in a diameter expansion direction acts also on the outside-diameter side member. This pressing force is converted by a contact angle of the rolling members into a component in an axial-direction, and the component acts in a direction to tighten the bearing clearance, giving preload to the bearing. In this case, preload control is facilitated because an amount of preload can be directly set at any value by the adjustment of pressing force acting in the diameter-expansion direction.
Hardening of the irregular portion described above is preferably made by a heat treatment using induction heating such as induction quenching (induction heat treatment). An induction heat treatment enables local heating as well as free selection of a depth of a hardened layer. Further, the treatment is advantageous in that it can be controlled so as not to significantly thermally affect areas other than the hardened layer, so that characteristics of a base material is maintained unchanged.
Setting the difference in hardness between the irregular portion and the low hardness portion at HRc 30 or more can securely prevent crushing of the irregular portion at the time of swaging.
Because the irregular portion is formed at an inside periphery of the outside-diameter side member, working the portion with high accuracy is difficult. Therefore, selection of a working method is an essential point. In this case, the irregular portion can be effectively formed with high accuracy with processes including broaching, particularly with helical broaching repeated a plurality of times.
When the irregular portion is formed by grooves in a plurality of rows made to cross each other, fretting wear between the irregular portion and the low hardness portion in the axial direction or circumferential direction can be securely prevented.
The swaging described above is made by a swaging jig having a diameter larger than that of an inside diameter of the inside-diameter side member. At this time, the swaging jig is made to slide on an inside periphery of the inside-diameter side member to expand in diameter the low hardness portion. In this case, the low hardness portion is preferably expanded in diameter by the swaging jig while the inside-diameter side member is being pushed into a direction of reducing an axial bearing clearance. With this method, because pressing force in the axial direction is given to the inside-diameter side member by the swaging jig, the inside-diameter side member and the outside-diameter side member can be joined by swaging while the axial bearing clearance is being reduced. Therefore, a necessary and sufficient amount of preload can be put in a simple process and preload control is facilitated.
Conventionally, as shown in FIG. 35, a stem portion 450 of the outer joint member 410 is first pressed into the inside of the hub ring 100. After that, with a bottom portion of the mouth portion 460 of the outer joint member 410 being supported by a receive member 520, a swaging jig 540, having a larger diameter than an inside diameter of the stem portion 450 of the outer joint member 410, is pressed into the inside of the stem portion 450 in the direction of the arrow to partly expand a diameter of the stem portion 450 (Japanese Patent Laid-Open Publication No. 2001-18605). By doing so, pressing force in the axial direction of the swaging jig 540 is directly supported by the receive member 540 without allowing the pressing force to pass through the hub ring 100 at an outside-diameter side. With this method, however, a clearance T is produced after swaging at a butt portion between an end face of the hub ring 100 and a shoulder face 470 of the outer joint member 410 (see FIG. 36), and the clearance T may cause loss of preload, possibly affecting bearing rigidity or bearing endurance life.
On the other hand, the method according to the invention is, as an example in FIG. 22, a method of manufacturing a wheel bearing device comprising: an outer joint member 21 having outer raceways 24 in double rows on its inside periphery; an inner member 29 having inner raceways 27 and 28 in double rows facing to the outer raceways, an inside-diameter side member 61, and an outside-diameter side member 63 fitted onto the inside-diameter side member with an irregular portion 31 interposed in between; and rolling members 22 in double rows disposed between the outer raceways and inner raceways. With this method, the inside-diameter side member 61 is at least partly expanded in diameter by a swaging jig 54 pushed into the inside of the inside-diameter side member 61, so that the irregular portion 31 bites into its opposing face to join together by swaging the inside-diameter side member 61 and the outside-diameter side member 63. At this time, the inside-diameter side member 61 is expanded in diameter while being pressed by the swaging jig 54 toward axially one side with the inside-diameter side member 61 being made butt against axially the other side of the outside-diameter side member 63 and the outside-diameter side member 63 at the axially one side being supported by the receive member 52.
When the inside-diameter side member 61 is pressed toward the axially one side by the swaging jig 54, the outside-diameter side member 63 butting against the inside-diameter side member 61 is in turn pressed and pushed in to the same direction. In this Process, the outside-diameter side member 63 at the axially one side is supported by the receive member 52 and prevented from moving toward the direction of the axially one side. In other words, a pressing force in an axial direction of the swaging jig 54 is received and supported by the receive member 52 after passing through the inside-diameter side member 61 and then the outside-diameter side member 63. Consequently, clearance between both end faces of the inside-diameter side member 61 and the outside-diameter side member 63 is tightened at a butt portion 70 where the two members butt against each other, and compression strain remains at and around the butt portion 70. As a result, a distance L, indicated in FIG. 23(A), between the inner raceways 27 and 28 before the swaging is decreased by an amount of compression strain xcex4, indicated in FIG. 23(B), after the swaging (to become L-xcex4). Therefore, through the setting of this xcex4 at an appropriate value, a desired amount of preload can be given to the bearing with an axial bearing clearance being negative. After swaging, the inside-diameter side member 61 and the outside-diameter side member 63 are solidly joined together without loosening through the biting of the irregular portion 31 into the opposing face 36. Consequently residual compression strain does not disappear and initial preload is steadily maintained for a long period.
In this case, the amount of the compression strain xcex4 is dependent on a push-in force F of the swaging jig 54 (see FIG. 22) and also on rigidity of the inside-diameter side member 61 and outside-diameter side member 63, or more specifically rigidity at and around the butt portion 70 of both the members 61 and 63. Therefore, preload can be set in a most appropriate range by controlling the push-in force F.
To smoothly carry out the process described above, an outside diameter xcfx86A of the swaging jig 54, an inside diameter xcfx86B of the portion 34 to be swaged of the inside-diameter side member 61, and an inside diameter xcfx86C of the inside-diameter side member 61 excluding the portion 34 to be swaged are set at the relationship of xcfx86C greater than xcfx86A greater than xcfx86B.
The swaging jig 54 can also be of an expandable/reducible structure, By doing so, even the portion 34 to be swaged located at an opening side of a bottomed cylindrical member (such as the outer joint member 41 blocking a bottom of the mouth portion 46) as shown in FIG. 29 can also be swaged for joining. Specifically, the swaging jig 54 reduced to a diameter which is smaller than an inside diameter of the portion 34 to be swaged is inserted into the inside of the inside-diameter side member 41 (outer joint member) up to a position beyond the portion 34 to be swaged. Then, the swaging jig 54 is expanded in diameter to a dimension larger than that of the portion 34 to be swaged, and then the swaging jig 54 is drawn in the direction opposite to the insertion. Thus, with the same effect as described above, the inside-diameter side member 41 and the outside-diameter side member 10 (hub ring) can be securely swaged for joining,
The swaging jig can be, for example, composed in an expandable/reducible structure by taper-fitting of a divided punch divided in a circumferential direction and an insertion member slidably inserted into the inside of the divided punch.
The inside-diameter side member can be joined by swaging to the outside-diameter side member provided with the inner raceway. It can also be joined by swaging to the outside-diameter side member 71 (see FIG. 32) that is not provided with an inner raceway. In the latter case, deformation of the inner raceway cause by swaging can be prevented from occurring.
The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.